New species and record of Dodecaceria (Annelida: Cirratulidae) the Biological Reserve of Rocas Atoll, Brazil, the only atoll in the South Atlantic Ocean

The polychaete Family Cirratulidae is one of the most abundant and diverse groups of Annelida, although it remains poorly known worldwide. Dodecaceria Ørsted, 1843 is one of the least described genera of Cirratulidae. The present report is the first taxonomic study of the genus Dodecaceria for the Brazilian coast. Cirratulidae were collected at Rocas Atoll, the first Brazilian marine protected area and the only atoll in the South Atlantic Ocean. We described one new species, Dodecaceria zelinhae n. sp., and a new record of D. dibranchiata Blake & Dean, 2019, previously only known from Panama. The new species is distinguished from other Dodecaceria species by having lateral tentacles, a smooth peristomium, 3–5 pairs of branchiae, hooks from chaetiger 11 in notopodia and 9 in neuropodia. Dodecaceria dibranchiata, a Caribbean species, is here recorded for the first time in the South Atlantic Ocean.


Introduction
The polychaete Family Cirratulidae Ryckholt, 1851, is one of the most abundant and diverse groups of the phylum Annelida.Regarding genera composition within the Cirratulidae family, two perspectives differ in their number.Taxonomic studies indicate the existence of 11 genera [1], while recent phylogenetic studies include Ctenodrilinae Kennel, 1882 as a subfamily within Cirratulidae, totaling 16 genera [2].Cirratulids occur in all oceans and depths, on surfaces or sub-surfaces of soft bottoms, although some species of the genus Dodecaceria Ørsted, 1843 are found on hard bottoms [3].Initial inclusion of Cirratulidae in a sequence database (18S rRNA) occurred with Dodecaceria concharum, as documented by Winnepenninckx et al. in 1998 [4].This specific sequence was subsequently used to gain insights into the relationships among larger taxonomic groups within the phylum Annelida, playing a crucial role in the study of Annelida phylogeny [5,6].
Currently, Dodecaceria comprises approximately 20 valid species [1].The genus is a hard bottom cirratulid and is readily characterized, among other features, by having a single pair of dorsolateral tentacles, branchial filaments generally restricted to anterior chaetigers, and acicular hooks simple, spoon shaped, or sometimes serrated [7].
Like other cirratulids, the genus is confusing due to the superficial morphological similarity of species.Thus, for example, cirratulids lose important taxonomic characters during collection [3,8], such as in Dodecaceria, when frequently removed from their tubes, specimen handling can result in the fragmentation of the body at either the posterior or anterior end [9].Other factors that can contribute to taxonomic misidentification are reproductive characteristics.Dodecaceria species have a complex life cycle characterized by sexual and asexual reproduction [1], which often makes it difficult to correctly distinguish different states of development or stage of regeneration.
Studies of Dodecaceria are rare, and the majority of species described are found in the North Atlantic Ocean [1].Although there has been increasing work on the Cirratulidae in the South Atlantic Ocean [10][11][12][13][14], including Brazilian waters [12,13].However, Dodecaceria is poorly known in this region.Only three species were reported to the South Atlantic Ocean: Dodecaceria meridiana Elı ´as & Rivero, 2009 in the littoral of Argentina [14], D. capensis Day, 1961 was reported in a checklist by Praia do Seixas, Paraiba State [15], and Dodecaceria concharum Ørsted, 1843 in a master's thesis for the São Paulo coast [16].To date, no taxonomic work has been published for Dodecaceria in Brazil.
The present work reports Dodecaceria from Rocas Atoll, the only atoll in the South Atlantic Ocean and one of the world's smallest atolls [17].Rocas Atoll was designated a Brazilian Marine Conservation Unity in 1979 [18].The Biological Reserve of Rocas Atoll is a protected area where scientific research is the only permitted human activity [19].Herein, we describe a new species, Dodecaceria zelinhae n. sp., and a new record Dodecaceria dibranchiata Blake & Dean, 2019 from the Rocas Atoll.

Material and methods
The Biological Reserve of Rocas Atoll is located 266 km northeast of the coastal city of Natal, in the State of Rio Grande do Norte, and 148 km from the Fernando de Noronha Archipelago, in the State of Pernambuco (Fig 1A).The atoll has a volcanic origin and coralline formation, its largest axis is approximately 3.7 km long, and the shortest axis is 2.5 km long.There are two islands, Farol and Cemite ´rio, encompassing 7.2 km 2 of emerging area inside the atoll ring [20].Except for the two islands, the atoll area is submerged during high tides, and several pools are exposed during low tides (Fig 1B).Tide pools vary in depth from 0.5 m to more than 7 m [20].
The specimens of Dodecaceria were collected between 13 September and 5 October 2015.Samples of hard bottom were taken in areas mainly composed of coralline rocks in two different environments: hard bottoms near Farol Island (0-2 m depth) and a tidal pool named Piscina Podes Crer (0-7 m depth).Specimens were removed after manual fragmentation of hard bottom, and after fixed in 4% formalin in seawater and preserved in 70% ethanol.For a detailed observation of the characters, the specimens were examined and measured using the Zeiss Stemi SV 11 stereomicroscope and Zeiss Axio Lab A1 microscopes.In addition, selected specimens underwent scanning electron microscopy (SEM) at the Laborato ´rio de Imagem e Microscopia O ´ptica e Eletro ˆnica, Instituto de Biologia, Universidade Federal do Rio de Janeiro (UFRJ), using a HITACHI TM3030 plus scanning electron microscope.Specimens for SEM were dehydrated in a graded series of increasing concentrations of ethanol (92%), critical point-dried, and coated with ~35 nm of gold.The holotype and paratypes of the newly https://www.gov.br/cnpq/pt-br.Funders had no role in study design, data collection and analysis, decision to publish, or manuscript preparation.described species were deposited at the Annelida Collection of the Museu Nacional do Rio de Janeiro (MNRJP), UFRJ, Rio de Janeiro, Brazil.

Nomenclatural acts
The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature.Hence, the new names contained herein are available under that Code from the electronic edition of this article.This published work and the nomenclatural acts are registered in ZooBank.The ZooBank LSIDs (Life Science Identifiers) can be resolved, and the associated information viewed through any standard web browser by appending the LSID to the prefix 00 http://zoobank.org/ 00.The LSID for this publication is urn: lsid:zoobank.org:pub:EEBDA733-911F-4499-AF9D-52AED22A35CB.The electronic edition of this work was published in a journal with an ISSN, has been archived, and is available from the following digital repositories: PubMed Central, LOCKSS.

Systematics
Family Cirratulidae Ryckholt, 1851.Diagnosis.Body elongated, cylindrical.Thoracic region often expanded, abdominal region narrow or moniliform, sometimes expanded in the pre-pygidial region.Prostomium narrow and conical or wide, without appendages, eyespot present or absent, and dorsolateral paired nuchal organs.Peristomium smooth or with annular rings.Grooved tentacles present as a single pair or multiple from the peristomium or subsequent anterior chaetigers.Branchiae long, starting from the peristomium or first chaetigers, inserted dorsally and usually present up to the abdominal region.Parapodia birramous with rudimentary lobes.Chaetae simple, including capillaries, acicular spines, and bidentate or multidentate hooks.Pygidium with a simple lobe, sometimes with sub-anal disk or terminal cirrus.Pharynx ventral, unarmed [1].
Diagnosis.Prostomium conical or rounded on anterior margin, forming a hood over the mouth.Peristomium short or long, with or without annular rings.A pair of grooved tentacles arising laterally or dorsolaterally in the peristomium.One to several pairs of branchial filaments extending over one to few anterior segments.Chaetae simple, including capillaries and stout, and acicular hooks simple, chisel or spoon-shaped, or sometimes serrated [1].
Remarks.The taxonomy of the genus Dodecaceria poses difficulties, partly due to the loss of the type specimen and the limited description of the type species.Ørsted [7] provides a brief overview of the type species, Dodecaceria concharum, discovered in Danish waters, although specific details about the location and date of collection of the type specimens were n not specified.These challenges are further compounded by the confusion surrounding the taxonomic identification of Dodecaceria species.Not only is it challenging to determine morphological characters, but there has also been a historical lack of taxonomic information available for both the type species and subsequent species within the genus.Subsequently, Caullery and Mesnil [21] reported the presence of D. concharum in the commune La Hague, Manche, France, and the morphological examination of the specimens revealed the existence of three distinct morphotypes.Two of these morphotypes were later recognized as specimens of D. ater (Quatrefages, 1866) [22,23].Adding to the complexities of Dodecaceria taxonomy, many species of Dodecaceria exhibit different modes of asexual reproduction.This involves their remarkable ability to regenerate their entire bodies [22,23].Asexual reproduction in Dodecaceria occurs through intriguing mechanisms, such as regenerating body parts after fissioning.This process is also observed in other annelids, such as syllids [24,25].Examples of fission have been reported in several Dodecaceria species, including D. berkeleyi Knox, 1971 [26, 27], D. diceria Hartman, 1951 [28], D. fimbriata [29,30], D. meridiana [31], D. pulchra [23,32], D. sextentaculata [23], and D. concharum [21,22].In the case of D. concharum, the larger segments of the trunk break off individually and regenerate into new individuals [23].Due to the morphological differences that can occur during asexual reproduction or regeneration, there have been historical records of several misidentifications among Dodecaceria species.Consequently, Gibson [27] recommended that the taxonomy of the group should consider reproductive modes.Currently, the genus Dodecaceria comprises approximately 20 valid species [  Habitat.Coral reefs, 0-4 m depth [9].In the present study, hard bottom and coral reefs, intertidal depths.
Remarks.The specimens from Rocas Atoll have the same diagnostic characters as Dodecaceria dibranchiata Blake & Dean, 2019, including only two pairs of branchiae, from the peristomium and the first chaetiger, respectively.Additionally, the peristomium is smooth and elongate, and all hooks are spoon-shaped.D. dibranchiata was originally described from the Caribbean Sea (Panama) in coral reefs.The species Dodecaceria diceria Hartman, 1951 and Dodecaceria laddi Hartman, 1954 are also characterized by two pairs of branchiae.Dodecaceria diceria differs from D. dibranchiata from Rocas Atoll and D. dibranchiata by having hooks with small grooves in the geniculate region [33] Dodecaceria laddi differs from D. dibranchiata by having a transversal groove between the prostomium and the peristomium and an annular ring in the peristomium [34].Furthermore, the species differ in terms of habitat and type locality, D. diceria was described in association with gastropod shells off the coast of Florida collected 214 m deep [35].In comparison, D. dibranchiata from Rocas Atoll was collected on hard bottom and coral reefs in intertidal depths, and D. dibranchiata Blake & Dean, 2019 was described in association with corals off the coast of Panama 0-4 m deep [9].D. laddi was described from the Marshall Islands in the Pacific Ocean [34].In contrast, D. dibranchiata from Rocas Atoll, and D. dibranchiata Blake & Dean, 2019 were described and collected in the Atlantic Ocean.Morphological variation regarding the number of branchia pairs remains unclear for D. diceria due to the lack of information on the number of branchiae and examined specimens in the original description [33].A specimen (MNRJP-007565) exhibited a possible sign of regeneration, with a narrowing observed in chaetiger 19.Another evidence of regeneration was observed in D. dibranchiata from Rocas Atoll, as indicated by lighter pigmentation in the posterior and anterior ends in one specimen.The ability to perform anterior and posterior regeneration strongly suggests that this species can reproduce by paratomic fission.The process of asexual reproduction involving regeneration is already recognized in different other species of Dodecaceria, such as D. berkeleyi [26,27], D. concharum [21][22][23], D. meridiana [31], D. pulchra [23,32].This is the first record of regeneration and asexual reproduction for Dodecaceria dibranchiata.Variation in the number of pairs of branchiae: five (holotype), three (MNRJP-007568; MNRJP-007569), four (MNRJP-007569).
Specimens in regeneration.One specimen with anterior regeneration (Fig 4A and 4B), and one specimen with both anterior and posterior regeneration (MNRJP-007569).
Habitat.Hard bottom and coral, intertidal depths.Distribution.Presently known only from the Atlantic Ocean: Rocas Atoll (Brazil).
Remarks.Dodecaceria zelinhae n. sp. has a variable number of pairs of branchiae ranging from three to five.It is not unusual for Dodecaceria species to show variability in this character.For example, D. concharum Ørsted, 1843 from Denmark has 3-6 pairs, and D. meridiana Elı ´as & Rivero, 2009 from the Argentinian coast has 7-18 pairs (Table 1).A few species have Etymology.This species is named in honor of Maurize ´lia de Brito Silva (Zelinha), in recognition of her important work in protecting the Rocas Atoll.For over 30 years, she has been working for ICMBio as the head of the Rocas Atoll Biological Reserve.

Discussion
The systematics of the genus Dodecaceria have been constantly revised.Gibson [27] concluded that the pattern of branchiae and chaetae correlates with the specimens' size and proposed greater attention to the way of life and details of asexual reproduction for the genus.Differences in the stages of development or regeneration and reproductive strategies raised questions about synonyms or even misidentifications [37].Asexual reproduction and regeneration change individuals' morphology and, sometimes, even make it impossible to determine some characters, such as the number of branchiae, prostomium, and peristomial morphology.Aguillar-Camacho & Salazar-Vallejo [38] described Dodecaceria carolinae, proposing a diagnostic character for the genus, which is the presence of branchiae that are either monomorphic (i.e., of the same size) or dimorphic (i.e., of different sizes along the body).However, specimens collected at Rocas Atoll show different regenerative phases of the anterior region, which was reflected in the length of the branchiae.This observation is consistent with Gibson's findings on the reproductive modes of Dodecaceria species deposited in Museums [27].Therefore, we argue that this character can vary depending on the developmental stages of the individual, which differences in size and regenerative stage can illustrate.Current studies on the reproductive modes and ontogeny process of Dodecaceria species are needed to understand which branchiae related characters are most appropriate for identification at a specific level.
There are approximately 20 valid species of Dodecaceria [1].However, only six species of Dodecaceria are recorded in South Atlantic waters.On the Argentine coast, the species D. concharum [39,40] [15] and D. concharum [16], have been documented.The limited availability of taxonomic publications highlights the significance of having more studies that focus on the Brazilian coastline.Consequently, further investigations would be highly recommended to enhance our comprehension of these taxa.It is evident that there is a lack of knowledge regarding the diversity of the genus in the South Atlantic Ocean.The Brazilian and Argentine coasts, given the already known diversity of Cirratulidae, are considered potential areas with a high probability of harboring Dodecaceria species [31].
To date, the only Dodecaceria species described from oceanic islands is D. laddi, which was originally recorded in the Marshall Islands [34].No Dodecaceria species have been described from Oceanic islands in the South Atlantic prior to this study.It is already known that these islands exhibit high levels of endemism in marine taxa [42][43][44], and are important breeding sites [45][46][47][48].Despite the growing anthropic pressures [49], some of them still present coral reefs considered "pristine", for example, Rocas Atoll [50,51].
Before the present study, three Cirratulidae species had been documented in Rocas Atoll: Timarete caribous (Grube, 1859), Timarete punctata (Grube, 1859), and Timarete ceciliae Magalhães et al., 2014 [52].This research expands our understanding of Cirratulidae in the Atlantic and Rocas Atoll by presenting a new record of D. dibranchiata Blake & Dean, 2019, and the description of a new species.

Table 1 . Taxonomic characters for species of Dodecaceria.
[36] 1955mber of branchial pairs on the peristomium comparable to D. zelinhae n. sp.namely D. alphahelixae Blake & Dean, 2019 from the Caribbean Sea, Panama, with 2-4 pairs of branchiae; D. saeria Paterson & Neal 2020 from Malvinas islands, with 2-3 pairs of branchiae; and D. pulchraDay, 1955from Atlantic Ocean, South Africa, with 4-5 pairs of branchiae.Although this variation in branchial pairs is comparable in this species, other characteristics set them apart.While D. zelinhae n. sp. the first hooks occur on chaetiger 9, whereas D. alphahelixae and Dodecaceria saeria have their hooks from the chaetiger 5[9]and 22[35], respectively.Additionally, D. zelinhae n. sp. and D. alphahelixae have different peristomium morphology; the first has a smooth peristomium whereas the second has one annular ring.There are also differences in terms of habitats.In contrast to D. zelinhae n. sp. which is from shallow waters, D. saeria has been collected from depths greater than 450 m[33].Moreover, D. zelinhae n. sp.differs from D. pulchra on the presence of capillary chaetae.D. pulchra has capillary notochaetae and neurochaetae from chaetiger 1 to chaetigers 12-14; after chaetigers 12-14, only a variable number of subsequent chaetigers have capillary notochaetae, and capillary neurochaetae are absent[36].On the other hand, D. zelinhae n. sp. has capillary notochaetae in all chaetigers.Thus, D. zelinhae n. sp.differs from these similar species due to this combination of characters: hooks from chaetiger 11 in the notopodia, hooks from chaetiger 9 in the neuropodia, a smooth peristomium, and notochaetae present in all chaetigers.Notably, evidence of anterior regeneration was found in a specimen of D. zelinhae n. sp.This species can be distinguished by its anterior narrowing towards the head, which is unpigmented, in contrast to the rest of the body. variation